The purpose of this project is to investigate the mechanisms which control feeding behavior in normal and experimentally obese monkeys. The nature of the metabolic and hormonal signals involved in the control of ingestive behavior will be studied. Circulating hormones and metabolites, adipose tissue mass, gastrointestinal motility, and feeding behavior will be studied over five periods during the induction and remission of obesity: a) at normal body weight during normal feeding, b) during a period of intragastric overfeeding and progressive rapidly increasing bodyweight and adiposity, c) when obesity has been established and is being sustained by continued forced feeding, d) during the period of voluntary abstinence from food while body weight is decreasing toward normal, and e) in the period following stabilizing of body weight and the return of normal feeding. Under both normal and obese conditions, experiments will be conducted to further define the nature and mechanisms of a newly described phenomenon of sustained oscillations in plasma levels of insulin, glucagon and certain metabolites. These experiments will provide further data concerning the controls of the endocrine pancreas and feeding behavior. Results will contribute to the understanding of disturbances of feeding behavior and body weight, as well as the regulation of metabolism, and will have implications for the possible prevention or therapeutic management of obesity.